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Date of Award

Spring 2007

Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science

Department

Biology

First Advisor

Dr. April L. Hill

Second Advisor

Dr. Laura Runyen-Janecky

Abstract

Sponges are true animals and have many characteristics typically associated with more complex and derived species, however, they lack a nervous system, sensory organs, and a defined body axis. Due to their unique position in the evolution of animals, sponges provide insights into the nature of the function of genes that later became members of the complex sensory pathways. One such gene family is the Six (sine oculis) class of transcription factors, known to be involved in the developmental pathway leading to eyes in all animals. We have found a Sixl/2 gene in two species of sponge using degenerate PCR and bioinformatics searches. Since more complex animals possess many Six gene family members, our data supports the hypothesis that Sixl/2 was the ancestral gene that later became involved in the eye pathway. To give us a better understanding of the role of Sixl /2 predating involvement in eye development we have conducted temporal and spatial expression studies in sponges. Our RT-PCR studies have demonstrated that Sixl/2 is expressed throughout larval development and in fully developed adult tissue as well as being expressed in aggregated, disaggregated and spreading tissue and Through in situ hybridization we have shown that Sixl/2 is expressed in the ciliated columnar epithelial region of early larvae and in the atrial pinacoderm and regions surrounding choanocyte chambers of the adult sponge. Choanoctye chambers permit sponges to respond to external stimuli (acting as a primitive "sensory system") via the cessation of pumping activity. Collectively, this work provides a foundation for future studies aimed at testing the hypothesis that a role for the development of primitive eyes already existed in the most basal animals.

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